The present invention relates to an information transmission arrangement comprising at least a first and a second transceiver unit located in a propagation medium having an attenuation which varies as a function of a frequency used for the transmission, in which at least one of the units comprises
a send section to send useful information by means of a carrier signal centered on a carrier frequency established via a control oscillator comprising a frequency variation controller, PA0 a receive section to receive the useful information sent by means of the carrier signal. PA0 at least one of the units comprises a meter for measuring the level of the received carrier signal in order to influence the frequency variation controller of at least one of said control oscillators, PA0 and the frequency variation is selected to be situated in a zone where the attenuation of the propagation medium presents a steep attenuation gradient which is generally monotonic--that is, the attenuation varies substantially always in a given direction as frequency increases within the zone. PA0 the aerials have small dimensions and favourable directional characteristics, which is compatible with the requirements as to discretion, PA0 the selected frequency band provides a wide dynamic range of the received signal level which corresponds well with the first measure proposed by the invention.
and in which at least the other unit comprises:
The field of application considered more particularly within the scope of the invention is transmission by means of radio channels or radio relay systems.
Such an arrangement is described in the article entitled "23 GHz Radio Equipments DTS 10-64 and FTD 23" by P. MARCHAND and E. FERNANDEZ published in the journal "Communication and Transmission", No. 4, 1986.
Although it gives entire satisfaction, this described arrangement does not fulfil requirements as to discretion and resistance to the jamming imposed by tactical applications. Worded differently, the purpose of the radio relay link is to reach the transceiver unit to which it is directed, while avoiding being intercepted by a nonauthorized receive unit and avoiding a send unit jamming the transmission between two transceiver units forming part of the arrangement.